Method for producing grandular fertilisers

ABSTRACT

There is provided a method for producing granular fertilisers that includes at least one structural compound based on at least two salts. The method includes the steps of disposing of at least one salt that includes nitrogen, humidifying the at least one salt, mixing the at least one humidified salt with at least one substance comprising at least one alkaline and/or alkaline-earth element and/or at least one element of group IV, producing a granular fertiliser by granulation of the mixture, and cooling the granular fertiliser. There is also provided a granular fertiliser comprising nitrogen and having a pH in the range of 3≦pH≦7. The granular fertiliser shows a strength σ of σ≧3 MPa and includes a concentration c SC  of at least one structural compound with c SC ≧50 wt.-%.

The invention relates to a method for producing granular fertiliserscomprising structural compounds based on at least one salt according tothe preamble of claims 1 or 13. Further, the invention relates to agranular fertiliser according to the preamble of claim 34.

In particular, for producing complex granular fertilisers to be used inthe agriculture a broad assortment of fertilisers has to be provideddepending on the given usage conditions.

According to one known method for producing complex granularfertilisers, first, a mixture of starting materials is obtained. Thestarting material comprises usually ammonia. The mixture is then heatedto a temperature when it starts to melt. The molten starting materialsmixture is granulated in a further step. In consequence, a granularfertiliser is produced. The obtained fertiliser is then cooled,classified and packed.

Drawbacks of the method mentioned above are, first, a possible ammoniaevolution into a gas phase. Further, the technological set-up becomescomplex due to the necessity to use initial components only as solidsand the impossibility of return of absorbing solutions into the process.Such a method is described for example in the article “Obtaining ofNPK-fertilisers from ammonia phosphate and urea with added microelements” of E. Aasamae, E. Arumeel and M. Eeinard in Proc. Est. Acad.,Chem.—1992, 41, N4 pp. 164-168.

According to another method of producing complex granular fertilisers, amixture of the starting material with a humidity of 3 to 10 wt.-% isgranulated in the presence of alkaline, alkaline-earth elements andelements of group IV of the periodic system taken in an amount of 0.3 to6 wt.-% recalculated for elements (B. P. Sobolev, “Method of preparationof granular fertilisers”, the application for the invention N2000127782, priority from Aug. 11, 2000, Russia).

However, complex granular fertilisers produced according to knownmethods are strictly limited in view of the assortment range concerninglosses of ammonia, fluorine and other substances into a gas phase.Therefore, cleaning the effluent gases in the process and return of theproduced absorbing solutions into a technological process is necessary.As a result, the technological set-up becomes complicated andcumbersome. Further, a transition from production of one brand offertilisers to another one requires solving complex technologicalproblems.

In addition to technological problems, further requirements arise due tothe product's properties. Some brands of fertilisers have a highhygroscopicity. This is especially true in cases with excess ofnitrogen, or if carbamide is used. Moreover, such fertilisers aresusceptible to strong consolidation. Therefore, serious disadvantagesconcerning the applicability arise.

Multiple salts produced by applying certain compositions of thefertiliser to be prepared during the production process essentiallyimprove the physico-mechanical properties of the product. One reason forthe advantage of the multiple salts is that they contribute to theformation of structural compounds. With the term “structural compounds”salts are named that can be different in composition but that cancomprise the same substance. For example, water may be such substancethat may be present in the crystal lattice of the salt.

However, according to the known methods it is impossible to reach a highenough extent of formation of structural compounds based on at least twosalts to affect the range of issued production besides thephysico-mechanical properties of the fertilisers.

A further negative result is the limitation of productivity. Inaddition, only a small discharge of ammonia into a gas phase takesplace, which causes the necessity of using ammonia saltpetre only as asolution. Hence, the capability of obtaining fertilisers with increasedconcentration of nitrogen and further components is limited.

In view of the disadvantages given by known methods to produce granularfertilisers, mainly the following objects of the invention arise.

One problem to be solved by the invention is to produce much lesslimited assortment of granular fertilisers. Another problem to be solvedis to lift limitations on the productivity of the technological process.Further, ecological parameters of the production line have to beimproved.

Moreover, it is an object of the invention to improve thephysico-mechanical properties of the fertilisers. It is a further objectof the invention to increase the efficiency of the application ofalkaline, alkaline earth-elements and group IV elements.

It is another object of the invention to provide for obtaining differentbrands of fertilisers in a broad range of ratios and concentrations ofnutrient materials.

The above mentioned problems are solved by a method with the features ofclaims 1 or 13. Further, in claim 34, a granular fertiliser is providedwhich shows the objected properties. Advantages refinements are in eachcase given in properties. Advantages refinements are in each case givenin the dependent claims.

The solution according to the invention provides for the first time amethod for producing granular fertilisers comprising structuralcompounds based on at least two salts with the steps of disposing of atleast one salt comprising nitrogen, humidifying the at least one salt,mixing the at lease one humidified salt with at least one substancecomprising alkaline and/or alkaline-earth element and/or at least oneelement of group IV, producing a granular fertiliser by granulation ofthe mixture, and cooling the granular fertiliser.

One important advantage of the method is the efficient utilisation ofsubstances based on alkaline, alkaline-earth elements and/or group IVelements. These elements form structural compounds based on at least twosalts. Therefore, the method according to the invention provides forrealising the desired physico-mechanical properties of the product in asurprisingly simple way.

The formation of structural compounds based on at least two salts isaccompanied by heat evolution in the chemical process. The multiplesalts produced in the exothermic chemical reaction provide for the greatadvantage of improving the physico-mechanical properties of thefertiliser. According to the invention, the process step of coolinggives possibility of adopting the method in a surprisingly simple wayeven to extremely different requirements.

To ensure a pre-defined size scale of the product, according to theinvention the method further comprises the step of classification of thegranular fertiliser. To run the process advantageously even moreefficiently, the invention provides for feeding at least a part of thefine portion obtained by classification back into the process as aso-called recycle.

The method according to the invention allows to improve thephysico-mechanical properties of the fertilisers in view of a lowhygroscopicity and a minor chance of undergoing solidification. Furtherit is advantageously possible to adjust the ratio and concentration ofnutrient elements in the produced fertilisers in a broad range.

Thus, lifting limitations on the product yield due to prevention ofammonia discharge and return of absorbing solutions into the process arelifted are possibly by means of the invention. In addition,advantageously the ecological safety of fertiliser production isincreased.

Moreover, flexibility of the process in changing of the production fromone brand of fertiliser to another one is provided by the advantageouslysimple technological scheme. In consequence, capital costs inconstruction of the production line and manufacturing service costs arereduced.

The granulation itself can be carried out by any known method. If thegranulation is carried out in an drum granulator, then the steps ofmixing, granulation and cooling may be combined in a single apparatus.

If the granulation, however, is carried out in a plate granulator,according to the invention the steps of mixing, granulation and coolingcan also be carried out in different apparatuses. Already the steps ofmixing and granulation can be superimposed by the chemical reaction offorming the granular fertiliser. The actual reaction, however, activelyproceeds during the cooling step.

The method according to the invention provides for the great advantageof being flexible in view of the starting material. In particular, atleast one further salt comprising nitrogen can be fed into the process.Preferably, the at least one salt comprising nitrogen and/or the atleast one further salt comprising nitrogen comprise ammonium sulphateand/or ammonium phosphate and/or diammonium phosphate and/or ammoniumsaltpetre.

As explained above, according to the invention the advantageousphysico-mechanical properties of the product are mainly achieved byforming structural compounds. In order to do so, the invention providesfor the humidifying step. In particular, by humidifying the at least onesalt comprising nitrogen and/or the at least one further salt comprisingnitrogen, a solution and/or pulp of salt is produced.

Preferably, the concentration c of the solution and/or pulp comprisingthe at least one salt comprising nitrogen and/or the at least onefurther salt comprising nitrogen is equal or greater than 40 wt.-%.Preferably, the concentration c of the solution and/or pulp is in therange of 75 wt.-% ≦c≦95 wt.-%.

For realising the desired physico-mechanical properties of thefertiliser provided by the structural compounds, according to theinvention adjusting of the humidity is one surprisingly simplepossibility. Therefore, the invention advantageously provides a humidityφ_(SP) of the solution and/or pulp comprising the at least one saltcomprising nitrogen in the range of 3 wt.-% ≦φ_(SP)≦30 wt.-%. Inaddition the invention provides a humidity φ_(S) of a salt being equalto or greater than 10 wt.-%.

On the contrary to known methods for producing granular fertilisers bymelting the starting material, the method according to the inventionprovides for the possibility of reducing the process temperaturesignificantly. In particular, the temperature

_(SP) of the solution and/or pulp comprising the at least one saltcomprising nitrogen is in the range of 75° C.≦

_(SP)≦95° C. Preferably, the temperature

_(SP) is in the range of 80° C.≦

_(SP)≦85° C. Thus, the energy consumption can advantageously besignificantly reduced in a process carried out according to the methodof the invention.

The method according to the invention further allows to adopt theproduct to a broad range of pH values. In particular, the pH of thesolution and/or pulp comprising the at least one salt comprisingnitrogen is in the range of 1.5≦pH ≦8, preferably in the range of4≦pH≦5.

The invention is not limited to the above described method for producinggranular fertilisers starting with disposing of at least one saltcomprising nitrogen and humidifying the at least one salt. Moreover, theinvention also provides an alternative method for producing thefertilisers comprising at least one structural compound with thefollowing steps: disposing of at least one mineral substance,de-composing the at least one mineral substance in particular byprecipitation using an asset, separating the remaining acidic liquorfrom the precipitate, ammonising the remaining acidic liquor, adding atleast one substance comprising at least one alkaline and/oralkaline-earth element and/or at least one element of the first periodof group IV to the ammonised acidic liquor, evaporating the surplus ofmoisture, producing a granular fertiliser by granulation of the mixture,and cooling the granular fertiliser.

By providing the possibility of using a mineral substance as a startingmaterial, the invention advantageously opens up the possibility ofpractically not being limited in the choice of the starting material.

The alternative method of carrying out the invention can also comprisethe further step of classification of the granular fertiliser in orderto ensure a predetermined size range of the product. Further, at least apart of the fine portion obtained by classification can be fed back intothe process as recycle.

In particular, the at least one mineral substance can comprise apatite,which is in a surprisingly simple way

In general, in the method according to the invention the ratio M of themass flow of recycle referred to the entire mass flow of the product isequal to or below 40 wt.-%. By controlling this parameter, the advantageof carrying out the whole process extremely efficiently is given.

The method of the invention is, further, not generally limited to theprocess steps mentioned above. In particular, single steps can becarried out more than once. In addition, the sequence of the processsteps may be varied in any desired way.

In detail, the method according to the invention can comprise a firstfurther step of mixing being carried out after adding the at least onesubstance comprising an alkaline and/or alkaline-earth element and/or atleast one element of group IV.

Moreover, at least one further salt can be fed into the process. Inparticular, the at least one further salt comprises carbamide and/orpotassium chloride and/or sodium chloride. Hence, further nutrients aswell as further components forming the structural compounds can be fedinto the process while a precise dosage and controlling of the mixture'sproperties are ensured by feeding several salts each in a single way.

To further contribute to the wide variety of ways to carry out themethod according to the invention, a second further step of mixing canbe carried out after feeding the at least one further salt into theprocess.

For optimising the conditions of forming granular fertilisers comprisingthe advantageous structural compounds, in the method according to theinvention the temperature

_(G) during the granulation is in the range of 45° C.≦

_(G)≦85° C., preferably in the range of 80° C.≦

_(G)≦85° C.

Already during the production of the granular fertilisers, an increasedconsumption of moisture absorbed from environmental atmosphere into thestructural components is possible. In particular, the substances basedon alkaline, alkaline-earth and other elements for transformationundergo this consumption of moisture. Such an increased consumption ofmoisture has the disadvantage to at least partially counteract thesolution provided by the invention which ensures improvedphysico-mechanical properties of the product.

Hence, the method according to the invention further provides anadditional step of encapsulating the granular fertiliser and/or afurther component. By doing so, especially stocking of the unpackedproduct can advantageously avoided.

Preferably, a further component to be encapsulated can be a granularcomponent itself, in particular, prilled ammonium saltpetre and/orgranulated carbamide. By encapsulating ammonium saltpetre and carbamidewith the prepared solutions and/or pulps, the invention provides thegreat advantage of not only reducing hygroscopicity of these products,but also preventing ammonium saltpetre from inflammation and explosion.

In one embodiment of the invention, therefore, in the step ofencapsulating the solutions and/or pulps to be mixed with at least onesubstance comprising an alkaline and/or alkaline-earth element and/or atleast one element of group IV are used as a coating material.

To optimise the reliability of the process in view of forming thestructural compounds, in the method according to the invention thecooling rate C is in the range of 0.1 K min⁻¹≦C≦40 K min⁻¹.

A further possibility provided by the method according to the inventionis to feed at least one mineral acid into the process. In particular,the at least one mineral acid can comprise sulphuric acid and/orphosphoric acid and/or nitric acid. Preferably, the pH of the mixtureobtained by feeding the at least one mineral acid into the process iscontrolled by the amount of mineral acid added.

In addition, a further possibility of designing the method according tothe invention in view of the given requirements is to feed water intothe process.

For example, granulation is carried out by means of humidifying,moistening, respectively, of mixed powder materials with solutionsand/or pulps (slurries). Humidifying may for instance be carried outonly with water. However, in this case a large amount of water may beneeded resulting in a decrease of the concentrations of principlenutrient elements such as in particular N, P, and K.

Therefore, the preferred technological methods for preparing ahumidifying agent comprise a preparation of concentrated solutionsand/or pulps. The term “solution” refers to a solution of, for instance,ammonium saltpetre in water, or ammonium phosphate or ammonium sulphatein water, or ammonium saltpetre, ammonium phosphate, potassium chloridein water, or carbamide, ammonium phosphate in water and so on.

To cover an as wide as possible range of compositions of the producedgranular fertiliser, in the method according to the invention a furtherstep of adding at least one nutrient can be carried out. In particular,this nutrient can comprise calcium, magnesium, iron, sulphur, boron,zinc, copper, manganese, and molybdenum.

As explained above, the product strength depends on the cooling rate ofthe fertiliser after the granulation stage. Heat produced in theexothermic chemical reaction is dissipated by cooling. Hence, by coolingthe formation of structural compounds is encouraged.

If the formation reaction of the structural compounds proceeds notcompletely during carrying out the process, the invention provides thepossibility of storing the product after the production. In particular,the method according to the invention can comprise the further step ofmaturating the product. Preferably, the maturation time t_(M) is equalto or less than 72 hours.

The invention further provides a granular fertiliser in particularproduced using a method as described above which comprises nitrogen andhas a pH in the range 3=pH=7.

The granular fertiliser according to the invention shows a strength σbeing equal to or greater than 3 MPa. The strength σ is the resistanceto pressure. The granular fertiliser shows an entire amount c_(SC) of atleast one structural component being equal to or greater than 50 wt.-%.

The concentration of the structural compounds is given in relation tothe theoretical concentration. The theoretical concentration can becalculated according to a chemical formula of the structural compound.For example, as a structural compound (NH₄)₂SO₄MgSO₄ is produced. Thisstructural compound should incorporate six water molecules. Hence, thequantity of moisture introduced into a process with solutions and/orpulps is known. After carrying out the process the concentration of freemoisture in the product is determined. Accordingly, the quantity of theformed structural compounds can be calculated.

According to the invention, the structural compound is based on amultiple salt comprising one further substance, in particular water. Asmultiple salts comprising in particular water, structural compounds cancomprise MgHPO₄nH₂O and/or NH₄MgPO₄nH₂O and/or (NH₄)₂SO₄Mg₂SO₄nH₂Oand/or NH₄NaHPO₄nH₂O.

To provide further nutrient components, the granular fertiliseraccording to the invention further comprises P₂O₅ and/or K₂O and/or SO₃.

In particular, a granular fertiliser can comprise nitrogen in the rangeof 10 wt.-% ≦c_(N)≦27 wt.-% and. P₂O₅ in the range of 6 wt.-%≦c_(P2O5)≦30 wt.-% and K₂O in the range of 6 wt.-% ≦c_(K2O)≦30 wt.-%.

The granular fertiliser according to the invention can alternativelycomprise nitrogen in a concentration of c_(N)=30 wt.-% and P₂O₅ with aconcentration of C_(P2O5)=5 wt.-%.

In a further alternative composition, the granular fertiliser cancomprise nitrogen with a concentration of c_(N)=28 wt.-% and SO₃ with aconcentration of c_(5O3)=3 wt.-%.

The invention is described below in view of preferred embodimentsreferring to the enclosed Figures.

The figures illustrate the following examples:

FIG. 1 one schematic flow chart of the method according to the inventionrealised in examples 1 and 2,

FIG. 2 one schematic flow chart of the method according to the inventionrealised in examples 3, 4, 5 and 6,

FIG. 3 one schematic flow chart of the method according to the inventionrealised in examples 7, 8, 9, 10, 11 and 12,

FIG. 4 one schematic flow chart of the method according to the inventionrealised in examples 13,

FIG. 5 one schematic flow chart of the method according to the inventionrealised in example 14,

FIG. 6 one schematic flow chart of the method according to the inventionrealised in example 15.

Examples 1 and 2 are illustrated in the flow chart schematically givenin FIG. 1.

EXAMPLE 1

A solution (pulp) on the basis of 17 g of ammonium sulphate with ahumidity of 30 wt.-%, a temperature 80° C., pH 1.5, and 29 g ammoniasaltpetre with a humidity of 3 wt.-% and a recycle are mixed in thepresence of 1.25 g of a substance recalculated for alkaline-earthmaterial. The mixture is granulated at the temperature of 75° C., cooledand classified. As a result, a product with a content of 2.8 wt.-% N,3.0 wt.-% S0₃ is prepared. The strength σ of the product is not lessthan 3.0 MPa, pH of the product is not less than 3.5. The concentrationof structural compounds is not less than 80 wt.-% from the amount whichis theoretically possible.

EXAMPLE 2

A solution (pulp) based an 17 g of ammonium sulphate with a humidity of30 wt.-%, a temperature of 85° C., a pH between 7 and 7.5, and 29 g ofammonia saltpetre with a humidity of 3 wt.-%, and recycle are mixed inthe presence of a substance of alkaline-earth material comprising atleast one alkaline-earth element taken in quantity 1.4 g recalculatedfor the given element. The mixture is then granulated at a temperatureof 65° C. Afterwards, the granulated product is cooled and classified.As a result, a product containing 28 wt.-% N and 2.5 wt.-% to 3.0 wt.-%S0₃ is obtained. The strength σ of the product is not less than 3.0 MPa.Its pH is in the range of 6.5 to 7. The concentration of structuralcompounds is not less than 87 wt.-% from the amount theoreticallypossible.

In table 1, an overview an the characteristics of the products and theircomposition as described in the examples is given. TABLE 1Characteristics of the products and their composition as described inexamples 1 to 15. Example σ/MPa pH C_(N)/wt.-% C_(P2O5)/wt.-%C_(K2O)/wt.-% C_(SO3)/wt.-% C_(SC)/wt.-% 1 3 6.5-7 28 — — 3 80 2 3 6.5-728 — — 3 87 3 3 5 14 14 14 — 93 4 3 6 10 30 10 — 85 5 3 6.5 17 17 17 —90 6 3 7 17 17 17 — 75 7 3 =5.5 27  6  6 — 75 8 3 5.5-6 10 30 10 — 90 93 6 15 15 15 — 85 10 3 6.5-7 10 10 10 — 98 11 3 =5.5 10 10 30 — 83 12 36 15 15 15 — 85 13 3 6 16 16 16 — 75 14 3 5 30  5 — — 70 15 3 =5.5 15 1515 — 80

The method carried out to realise examples 3 to 6 is illustrated by theschematic flow chart depicted in FIG. 2. The flow chart allows forfollowing the way through all the methods of those examples; the singlesteps shown in the figure do not necessarily have to be carried out ineach of the single methods given as examples.

EXAMPLE 3

A solution (pulp) based an 16 g of ammonium sulphate with a humidity of30 wt.-% and a temperature of 80° C. is mixed with 20 g of ammoniaphosphate with pH 7. In the next step carried out in example 3, 16.5 gof carbamide and 16 g of potassium chloride are added. In the presenceof 1.3 g of compounds of alkaline-earth element recalculated for thetaken element, the prepared ingredients are mixed with recycle andgranulated at 60° C. The granulated product is then cooled andclassified. As a result, the product contains 14 wt.-% N, 14 wt.-% P₂0₅,and 14 wt.-% K₂0. The strength of the product is not less than 3.0 MPa.The pH of a product is 5. The concentration of structural compounds isnot less than 93 wt.-% of the amount theoretically possible.

EXAMPLE 4

39 g of a pulp of ammonium phosphate with pH 5 and a humidity of 23wt.-% are mixed with 12 g of carbamide, 17 g of potassium chloride, 28 gof ammonium phosphate with pH 4.5 and the recycle. In the presence ofcompound of alkaline element taken in quantity of 2.4 g recalculated forthe taken element, the ingredients are mixed, granulated at thetemperature of 55° C., cooled and classified. As a result, the obtainedmaterial comprises 10 wt.-% N, 30 wt.-% P₂0₅, and 10 wt.-% K₂0. Thestrength of the product is not less than 3.0 MPa, the pH of the productis not less than 6.0. The concentration of structural compounds is notless than 85 wt.-% from the amount theoretically possible.

EXAMPLE 5

12.5 of a pulp of ammonium phosphate with pH 4.5 and a humidity of 20wt.-% and a temperature of 70° C. are mixed with 8.7 g of carbamide and8.7 g of potassium chloride and the recycle. In the presence of 0.75 gof a compound of alkaline element recalculated for the taken element,the obtained mixture is granulated at a temperature of 45° C., cooledand classified. As a result, the product contains 17 wt.-% N, 17 wt.-%P₂0₅ and 17 wt.-% K₂0. The strength of the prepared product is not lessthan 3.0 MPa, the pH of the product is not less than 6.5. Theconcentration of structural compounds is not less than 90 wt.-% from theamount theoretically possible.

EXAMPLE 6

A pulp prepared of 31 g of ammonium phosphate with pH 5 and 7.7 g ofwater, resulting in a humidity of 20 wt.-%, are mixed with 28 g ofpotassium chloride, 29 g of carbamide and recycle in the presence of asubstance containing 2.9 g of alkaline-earth material comprising atleast one alkaline-earth element. The obtained mixture is granulated ata temperature of 50° C., cooled and classified. The resulting productcontains 17 wt.-% of N, 17 wt.-% of P₂0₅, and 17 wt.-% of K₂O. Thestrength of the product is not less than 3.0 MPa, and its pH is 7. Thequantity of the structural compounds is no less than 75 wt.-% of theamount theoretically possible.

The method carried out to realise examples 7 to 12 is illustrated by theschematic flow chart depicted in FIG. 3. The flow chart allows forfollowing the way through all the methods of those examples; the singlesteps shown in the figure do not necessarily have to be carried out ineach of the single methods given as examples.

EXAMPLE 7

A quantity of 6 g of ammonium phosphate with pH 4.5 is mixed withsulphuric acid up to pH 1.5. Then, 0.6 g of ammonium sulphate is added.27 g of ammonia saltpetre with a humidity of 3.5 wt.-% and 13.3 g ofammonia saltpetre solution with a concentration of 85 wt.-% are preparedat the temperature of 80° C. to 85° C. In the presence of substanceswith alkaline-earth element taken in quantity 0.8 g recalculated forelement, the prepared ingredients and recycle are mixed, granulated atthe temperature of 70° C., cooled and classified. As a result, theproduct comprises 27 wt.-% N, 6 wt.-% P205 and 6 wt.-% K₂0. The strengthof the product is not less than 3 MPa, pH of the product is not lessthan 5.5. The concentration of structural compounds is not less than 75wt.-% from the amount theoretically possible.

EXAMPLE 8

A quantity of 58 g of ammonium phosphate pH in the range of 4.5 to 5 ismixed with 5.8 g of sulphuric acid. 18 g of a solution of ammoniasaltpetre with a concentration of 55 wt.-% to 60 wt.-% are prepared at atemperature of 90° C. In the presence of a compound of alkaline-earthelement taken in quantity 2.0 g recalculated for the taken element, theprepared ingredients are mixed with 17 g of potassium chloride andrecycle. Then, the mixture is granulated at a temperature of 65° C. As aresult, the product comprises 10 wt.-%, N, 30 wt.-% P₂0₅, and 10 wt.-%K₂0. Strength of, the product is not less than 3.0 MPa, pH of theproduct is 5.5 to 6. The concentration of structural compounds is notless than 90 wt.-% from the amount theoretically possible.

EXAMPLE 9

A quantity of 10 g of ammonium phosphate with pH 4.5 to 5 is mixed with1 g of sulphuric acid. Thus, a quantity of 13.3 g of a solution ofammonia saltpetre with a concentration of 85 wt.-% is prepared at atemperature of 75° C. In the presence of 0.6 g of substance ofalkaline-earth material comprising at least one alkaline-earth elementrecalculated for the taken element, the prepared ingredients are mixedwith 8.7 g of potassium chloride and recycle. Then, the mixture isgranulated at a temperature of 40° C. As a result, a product comprising15 wt.-% N,. 15 wt.-% P₂0₅, and 15 wt.-% K₂0 is prepared. The strength aof a product is not less than 3.0 MPa, pH of the product is 6. Theconcentration of structural compounds is not less than 85 wt.-% from theamount theoretically possible.

EXAMPLE 10

An amount of 58 g of ammonium phosphate with pH 4.5 to 5 is mixed with 5g of sulphuric acid. Thus, 18 g of a solution of ammonia saltpetre witha concentration of 55 to 60 wt.-% at the temperature of 90° C. areprepared. In the presence of 2.4 g of a compound with alkaline-earthelement recalculated for the taken element, the produced ingredients aremixed with 17 g of potassium chloride and recycle. Then, the mixture isgranulated at a temperature of 70° C. As a result, a product comprising10 wt.-% N, 30 wt.-% P₂0₅, and 10 wt.-% K₂0 is prepared. The strength aof the product is not less than 3 MPa, pH of the product is 6.5 to 7.The concentration of structural compounds is not less than 98 wt.-% fromthe amount theoretically possible.

EXAMPLE 11

A quantity of 19.2 g of ammonium phosphate with pH of 4.5 to 5 is mixedwith 1.9 g of sulphuric acid. 30 g of a solution of ammonia saltpetreand ammonium sulphate with a concentration of 87 wt.-% is prepared at atemperature of 80° C. In the presence of a compound of alkaline-earthelement taken in quantity 1.3 g recalculated for the taken element, theprepared ingredients are mixed with 50 g of potassium chloride andrecycle. Then, the mixture is granulated at a temperature of 60° C.,cooled and classified. As a result, a product comprising 10 wt.-% N, 10wt.-% P₂0₅, and 30 wt.-% K₂0 is obtained. The strength a of the productis not less than 3.0 MPa, pH of the product is not less than 5.5. Theconcentration of structural compounds is not less than 83 wt.-% referredto the amount theoretically possible.

EXAMPLE 12

A solution of ammonium saltpetre is prepared of 11.3 g of ammoniumsaltpetre, 1 g of ammonium sulphate and 2 g of water. The solution ismixed with 10 g of ammonium phosphate with a pH of 5, 8.6 g of potassiumchloride in the presence of a substance containing 0.55 g ofalkaline-earth material comprising at least one alkaline-earth elementand recycle. The prepared mixture is granulated at a temperature of 60°C., cooled and classified. The resulting product contains 15 wt.-% of N,15 wt.-% of P₂O₅, and 15 wt.-% of K₂O. The strength σ of the product isno less than 3.0 MPa and its pH is 6. The quantity of the structuralcompounds is not less than 85 wt.-% of the amount theoreticallypossible.

The method carried out to realise example 13 is illustrated by theschematic flow chart depicted in FIG. 4.

EXAMPLE 13

A pulp is prepared from 2.5 g of ammonium phosphate with a pH of 7, 1.6g of sulphuric acid, 6 g of carbamide, 1 g of ammonium sulphate and 1.5g of water in presence of a substance containing 0.4.g of alkaline-earthelement. The pulp is supplied for mixing with 7.5 g of diammoniumphosphate, 7.6 g of potassium chloride and recycle. The materialproduced is granulated at a temperature of 70° C., cooled andclassified. As a result, a product containing 16 wt.-% of N, 16 wt.-% ofP₂O₅, and 16 wt.-% K₂0 is prepared. The strength σ of the product is notless than 3.0 MPa, pH of the product is 6. The concentration of thestructural compounds is not less than 75 wt.-% of the amounttheoretically possible.

The method carried out to realise example 14 is illustrated by theschematic flow chart depicted in FIG. 5.

EXAMPLE 14

A pulp is prepared of 7.5 g of diammonium phosphate, 2.2 g of sulphuricacid, 1.5 g of sodium chloride, 20 g of ammonium saltpetre, 2.5 g ofwater and recycle in the presence of substance containing 0.5 g ofalkaline-earth element. The pulp is supplied for mixing and granulationwith prilled ammonium saltpetre. Encapsulating is performed at atemperature of 75° C. The material produced is cooled and classified. Asa result, a product comprising 30 wt.-% of N, and 5 wt.-% of P₂O₅ isobtained. The strength σ of the product is, not less than 3 MPa, its pHis 5. The concentration of the structural compounds is not less than 70wt.-% of the amount theoretically possible.

The method carried out to realise example 15 is illustrated by theschematic flow chart depicted in FIG. 6.

EXAMPLE 15

A quantity of 43 g of apatite is decomposed with 62.5 g of nitric acid.The formed calcium nitrate is separated. The produced acidic liquor isammonised to pH 2.5 to 3.5. Then, in the presence of a substancecontaining 0.8 g of alkaline-earth element the ammonised acidic liquoris evaporated. In a further step, it is granulated with recycle and 25.4g of potassium chloride at a temperature of 90° C., cooled andclassified. The resulting product comprises 15 wt.-% N, 15 wt.-% P₂O₅,and 15 wt-% K₂O. The strength σ is not less than 3.0 MPa, the pH of theproduct is not less than 5. The quantity of the structural compounds isnot less than 80 wt-% of the amount theoretically possible.

List of Symbols

-   c concentration-   c_(K2O) concentration of K₂O-   c_(N) concentration of nitrogen-   c_(P2O5) concentration of P₂O₅-   c_(SC) concentration of structural compounds-   c_(SO3) concentration of SO₃-   C cooling rate-   M ratio of the mass flow of the recycle referred to the entire mass    flow of the product-   φ_(S) humidity of a salt-   φ_(SP) humidity of a solution and/or pulp-   temperature-   _(G) temperature during granulation-   σ product's strength=resistance to pressure-   t_(M) maturation time

1. A method for producing granular fertilisers having at least onestructural compound based on at least one salt, comprising: disposing ofthe at least one salt, wherein the at least one salt comprises nitrogen,and wherein the at least one salt is selected from the group consistingof at least one first salt, at least one further salt, and a combinationthereof; humidifying the at least one salt; producing a mixture bymixing the at least one salt with at least one substance comprising anelement selected from the group consisting of an alkaline element, analkaline-earth element, an element of group IV, and any combinationsthereof; granulating the mixture to produce a granular fertiliser; andcooling the granular fertiliser.
 2. The method according to claim 1,further comprising classifying the granular fertiliser.
 3. The methodaccording to claim 2, further comprising feeding at least a part of afine portion, obtained by classifying, into the method as a recycle. 4.The method according to claim 1, further comprising feeding at least onefurther salt that comprises nitrogen into the method.
 5. The methodaccording to claim 1, wherein the at least one salt comprises asubstance selected from the group consisting of ammonium sulphate,ammonium phosphate, diammonium phosphate, ammonium saltpetre, and anycombinations thereof.
 6. The method according to claim 1, furthercomprising producing a solution and/or pulp by humidifying the at leastone salt.
 7. The method according to claim 6, wherein the solutionand/or pulp has a concentration c that is at least 40 wt.-%.
 8. Themethod according to claim 7, wherein the concentration c of the solutionand/or pulp is in a range of 75 wt.-% ≦c≦95 wt.-%.
 9. The methodaccording to claim 6, wherein the solution and/or pulp has a humidityφ_(SP) in a range of 3 wt.-% ≦φ_(SP)≦30 wt.-%.
 10. The method accordingto claim 1, wherein the at least one salt has a humidity φ_(S) that is10 wt.-%.
 11. The method according to claim 6, wherein the solutionand/or pulp has a temperature

_(SP) that is in a range of 75° C.≦

_(SP)≦95° C.
 12. The method according to claim 6, wherein the solutionand/or pulp has a pH that is in the range of 1.5≦pH≦8.
 13. A method forproducing a granular fertiliser having at least one structural compoundbased on at least one salt, comprising: disposing of at least onemineral substance; decomposing the at least one mineral substance, byprecipitation using an acid, forming a precipitate; separating aremaining acidic liquor from the precipitate; ammonising the remainingacidic liquor; producing a mixture by adding at least one substanceselected from the group consisting of an alkaline element, an alkalineearth element, an element of group IV, and any combinations thereof, tothe ammonised acidic liquor; evaporating a surplus of moisture;granulating the mixture to produce a granular fertiliser; and coolingthe granular fertiliser.
 14. The method according to claim 13, furthercomprising classifying the granular fertiliser.
 15. The method accordingto claim 14, further comprising feeding at least a part of a fineportion, obtained by classifying, into the method as a recycle.
 16. Themethod according to claim 13, wherein the at least one mineral substancecomprises apatite.
 17. The method according to claim 3, wherein therecycle has a ratio M of a mass flow that to an entire mass flow of thegranular fertilizer is up to 40 wt.-%.
 18. The method according to claim13, further comprising mixing after adding the at least one substance.19. The method according to claim 13, further comprising feeding atleast one further salt into the method.
 20. The method according toclaim 19, wherein the at least one further salt is selected from thegroup consisting of carbamide, potassium chloride, sodium chloride, andany combinations thereof.
 21. The method according to claim 19, furthercomprising mixing after feeding the at least one further salt into themethod.
 22. The method according to claim 1, wherein during granulatinga temperature

_(G) is in a range of 45° C.≦

_(G)≦85° C.
 23. The method according to claim 1, further comprising thestep of encapsulating a component selected from the group consisting ofthe granular fertiliser, a further component, and a combination thereof.24. The method according to claim 23, wherein the further component is agranular component.
 25. The method according to claim 23, wherein thestep of encapsulating comprises using solutions and/or pulps, that aremixed with the at least one substance, as a coating material.
 26. Themethod according to claim 1, wherein cooling the granular fertilizer isperformed at a cooling rate C in the range of 0.1 K min⁻¹≦C≦40 K min⁻¹.27. The method according to claim 13, wherein at least one mineral acidis fed into the method.
 28. The method according to claim 27, whereinthe at least one mineral acid is selected from the group consisting ofsulphuric acid, phosphoric acid, nitric acid, and any combinationsthereof.
 29. The method according to claim 27, wherein by feeding the atleast one mineral acid into the method obtains a mixture with a pH thatis controlled by an amount of the mineral acid added.
 30. The methodaccording to claim 1, further comprising feeding water into the method.31. The method according to claim 1, further comprising adding at leastone nutrient.
 32. The method according to claim 1, further comprisingmaturating the granular fertilizer.
 33. The method according to claim32, wherein maturating has a maturation time t_(M) that is to 72 h. 34.Granular fertiliser produced using a method according to claim 1,comprising nitrogen and having a pH in the range of 3≦pH≦7, wherein thegranular fertiliser has a strength σ of at least 3 Mpa and an entireamount c_(SC) of at least one structural compound that is at least 50wt.-%.
 35. The granular fertiliser according to claim 34, wherein thestructural compound is based on a multiple salt having one furthersubstance.
 36. The granular fertiliser according to claim 35, whereinthe structural compound is selected from the group consisting of MgHPO₄n H₂O, NH₄MgPO₄ n H₂O, (NH₄)₂SO₄Mg₂SO₄ n H₂O, NH₄NaHPO₄ n H₂O, and anycombinations thereof.
 37. The Granular fertiliser according to claim 34,further comprising at least one further component selected from thegroup consisting of P₂O₅, K₂O, SO₃, and any combinations thereof. 38.The granular fertiliser according to claim 37, further comprising anitrogen concentration c_(N) in the range of 10 wt.-% ≦c_(N)≦27 wt.-%, aP₂O₅ concentration c_(P2O5) in the range of 6 wt.-% ≦c_(P2O5)≦30 wt.-%,and a K₂O concentration C_(K2O) in the range of 6 wt.-% ≦c_(K2O)≦30wt-%.
 39. The granular fertiliser according to claim 37, furthercomprising a nitrogen concentration c_(N)=30 wt.-% and a P₂O₅concentration c_(P2O5)=5 wt-%.
 40. The granular fertiliser according toclaim 37, further comprising a nitrogen concentration c_(N)=28 wt.-% anda SO₃ concentration c_(SO3)=3 wt.-%.
 41. The method according to claim11, wherein the solution and/or pulp has a temperature

_(SP) that is in a range of 80° C.≦

_(SP)≦85° C.
 42. The method according to claim 15, wherein the recyclehas a ratio M of a mass flow that to an entire mass flow of the granularfertilizer is up to 40 wt.-%.
 43. The method according to claim 22,wherein during granulating a temperature

_(G) is in a range of 80° C.≦

_(G)≦85° C.
 44. The method according to claim 13, wherein duringgranulating a temperature

_(G) is in a range of 45° C.≦

_(G)≦85° C.
 45. The method according to claim 44, wherein duringgranulating a temperature

_(G) is in a range of 80° C.≦

_(G)≦85° C.
 46. The method according to claim 24, wherein the furthercomponent is selected from the group consisting of prilled ammoniumsaltpetre, granulated carbamide, and a combination thereof.
 47. Themethod according to claim 13, further comprising the step ofencapsulating a component selected from the group consisting of thegranular fertiliser, a further component, and a combination thereof. 48.The method according to claim 47, wherein the further component is agranular component.
 49. The method according to claim 48, wherein thefurther component is selected from the group consisting of prilledammonium saltpetre, granulated carbamide, and a combination thereof. 50.The method according to claim 47, wherein the step of encapsulatingcomprises using solutions and/or pulps, that are mixed with the at leastone substance, as a coating material.
 51. The method according to claim13, wherein cooling the granular fertilizer is performed at a coolingrate C in the range of 0.1 K min⁻¹≦C≦40 K min⁻¹.
 52. The methodaccording to claim 13, further comprising feeding water into the method.53. The method according to claim 13, further comprising adding at leastone nutrient.
 54. The method according to claim 31, wherein the at leastone nutrient is selected from the group consisting of calcium,magnesium, iron, sulphur, boron, zinc, copper, manganese, molybdenum,and any combinations thereof.
 55. The method according to claim 53,wherein the at least one nutrient is selected from the group consistingof calcium, magnesium, iron, sulphur, boron, zinc, copper, manganese,molybdenum, and any combinations thereof.
 56. The method according toclaim 13, further comprising maturating the granular fertilizer. 57.Method according to claim 56, wherein maturating has a maturation timet_(M) that is up to 72 h.
 58. The granular fertiliser according to claim35, wherein the one further substance is water.
 59. Granular fertiliserproduced using a method according to claim 13, comprising nitrogen andhaving a pH in the range of 3≦pH≦7, wherein the granular fertiliser hasa strength σ of at least 3 Mpa and an entire amount c_(SC) of at leastone structural compound that is at least 50 wt.-%.
 60. The granularfertiliser according to claim 59, wherein the structural compound isbased on a multiple salt having one further substance.
 61. The granularfertiliser according to claim 60, wherein the one further substance iswater.
 62. The granular fertiliser according to claim 60, wherein thestructural compound is selected from the group consisting of MgHPO₄ nH₂O, NH₄MgPO₄ n H₂O, (NH₄)₂SO₄Mg₂SO₄ n H₂O, NH₄NaHPO₄ n H₂O, and anycombinations thereof.
 63. The Granular fertiliser according to claim 59,further comprising at least one further component selected from thegroup consisting of P₂O₅, K₂O, SO₃, and any combinations thereof. 64.The granular fertiliser according to claim 63, further comprising anitrogen concentration c_(N) in the range of 10 wt.-% ≦c_(N)≦27 wt.-%, aP₂O₅ concentration c_(P2O5) in the range of 6 wt.-% ≦c_(P2O5)≦30 wt.-%,and a K₂O concentration C_(K2O) in the range of 6 wt.-% ≦c_(K2O)≦30wt-%.
 65. The granular fertiliser according to claim 63, furthercomprising a nitrogen concentration c_(N)=30 wt.-% and a P₂O₅concentration c_(P2O5)=5 wt-%.
 66. The granular fertiliser according toclaim 63, further comprising a nitrogen concentration c_(N)=28 wt.-% anda SO₃ concentration c_(SO3)=3 wt.-%.
 67. The method according to claim12, wherein the pH of the solution and/or pulp is in the range of4≦pH≦5.
 68. The method according to claim 4, wherein the at least onefurther salt is selected from the group consisting of carbamide,potassium chloride, sodium chloride, and any combinations thereof. 69.The method according to claim 4, further comprising mixing after feedingthe at least one further salt into the method.